This invention relates to a liquid reactant metal treatment system. More particularly, the invention relates to an apparatus and method for treating containerized feed materials without having to first remove the materials from the containers.
Many types of hazardous wastes or other waste materials are collected in drums, barrels, boxes, or other containers for long term storage. These containers of materials are often collected and stored pending a decision as to the appropriate disposal method for the materials. Very large quantities of some types of wastes have collected in storage because there has simply been no viable disposal alternative. This is particularly true for the vast quantities of mixed wastes which include halogenated hydrocarbons and other toxic materials mixed with high and low level radioactive materials, or nonhazardous materials that have been contaminated with hazardous and/or radioactive materials. Containerized wastes not only present the problem of disposing of the collected waste material itself, but also present the problem of either treating or disposing of the containers which have themselves become contaminated.
It is known that certain chemically active or reactant metals held as a liquid at elevated temperatures have the ability to chemically reduce organic compounds including hazardous compounds such as halogenated hydrocarbons. Suitable reactant metals include aluminum, magnesium, lithium, and alloys of these metals as described in U.S. Pat. Nos. 5,000,101, 6,069,290, and 6,355,857 to Wagner. The entire content of each of these prior patents is hereby incorporated in this disclosure by this reference. These liquid reactant metals chemically reduce organic molecules to produce mostly hydrogen and nitrogen gas, elemental carbon, char, and metal salts. Most metals mixed with the organic materials or bound up in organic molecules in the waste materials dissolve or melt into the liquid reactant metal. Low boiling point metals such as Mercury may go to a gaseous state and separate from the liquid reactant metal with other gases. Other metals alloy with the liquid reactant metal or separate from the liquid reactant metal by gravity separation.
A consistent issue in waste treatment processes utilizing a bath of a liquid reactant metal is ensuring sufficient contact between the liquid reactant metal and the waste material itself or intermediate compounds generated from initial reactions between the waste material and liquid reactant metal. Although in some cases, it may be desirable to control the reactions with the liquid reactant metal to prevent the feed material from being fully reduced, it is desirable in treating most waste materials to ensure sufficient contact with the liquid reactant metal to completely reduce the feed material. The problem of providing the required contact time is particularly acute with gaseous or volatile materials because such materials quickly separate from the liquid reactant metal and produce a bubble at the top of the liquid reactant metal container. The separated material must generally be forced again into the liquid reactant metal to allow the reduction reactions to continue, or more rapidly continue. U.S. Pat. No. 6,227,126 to Wagner is directed to an apparatus and process for treating gaseous and volatile material in a liquid reactant metal. In this system, the feed material is injected into a treatment chamber and the flow or passage of gasses and reactant metal through the reaction chamber is manipulated to mix the respective materials and ensure sufficient contact to completely reduce the gaseous materials.
U.S. Pat. No. 5,452,671 is directed to an apparatus and process for using a liquid reactant metal to destroy highly hazardous liquid and gaseous compounds, particularly materials used as chemical weapons or used to produce chemical weapons. This patent discloses treating a canister of hazardous materials by dunking the canister into a liquid metal bath and holding the canister under the surface of the liquid reactant metal. The patent discloses a unique dunking mechanism that forces gasses escaping from the submerged container to collect at different collection points within the liquid reactant metal and follow a tortuous path through the liquid reactant metal before reaching the uppermost surface of the reactant metal. Forcing gasses to follow this tortuous path through the various subsurface collection points was intended to provide the desired contact between the reactant metal and chemicals in the gas. Although this dunking arrangement may be suitable for many applications, there remains a need for an apparatus and process for treating containerized feed materials in a liquid reactant metal so as to ensure sufficient contact between the liquid reactant metal and the feed material/intermediate reaction products to allow the desired reduction reactions to proceed to completion.
An apparatus according to the invention includes a liquid reactant metal containment vessel for containing a first liquid reactant metal and isolating the reactant metal from the atmosphere. The apparatus further includes a release chamber adapted to receive the first liquid reactant metal from the containment vessel. A submerging or dunking arrangement included in the apparatus is adapted to dunk or submerge a container of feed material into the liquid reactant metal and move the container to a release location within or adjacent to the release chamber. Relatively light materials rising from the submerged container, including unreacted feed material, intermediate reaction products, and perhaps final reaction products, collect in a collection area having an upper surface defined by an upper surface of the release chamber. A treatment arrangement included in the apparatus places the fluids collected in the collection area in contact with the first liquid reactant metal or a second liquid reactant metal for a sufficient period of time to effect the desired reduction reactions.
The present invention has the advantage that the containers of feed material can be treated as a unit and the feed material is preferably not released from the container prior to introducing the material into the liquid reactant metal. Feed material is reduced to innocuous compounds or elements. Hazardous elements such as radioactive elements and other metals are captured in the liquid reactant metal or in a slag in the reactor. The containers themselves are also destroyed either by chemical reduction in the case of plastic or paper containers, or by melting or dissolution in the case of metal containers.
The term xe2x80x9cfeed materialxe2x80x9d will be used in this disclosure and the accompanying claims to describe the material to be treated in the apparatus and process of the present invention. Feed material may be homogenous or may be made up of mixtures of materials including nonhazardous materials, hazardous materials, or materials contaminated with hazardous materials. xe2x80x9cIntermediate reaction productsxe2x80x9d will refer to partially chemically reduced materials produced in the course of reducing the feed materials. xe2x80x9cFinal reaction productsxe2x80x9d will refer to materials resulting from the complete reduction of the feed materials by reaction with the liquid reactant metal. It will be appreciated that the containers used to contain feed materials may be plastic drums or barrels, metal drums or barrels, paper or cardboard containers, or any other type of container that may be used to hold or contain feed materials for treatment in the present apparatus.
In one variation of the invention, the submerging arrangement includes a dunking member adapted to extend along an inclined path from a container feed area within the liquid reactant metal containment vessel to the release location within the release chamber. In this variation of the invention the release chamber is defined between an inlet opening and an outlet opening. The collection area includes an area defined between an upper inlet opening level and an interior boundary of the release chamber at a level above the upper inlet opening level. The treatment arrangement in this variation of the present invention includes a pump or other device for inducing a flow of liquid reactant metal through the release chamber and a retention or treatment chamber. The treatment chamber is connected to receive the flow of reactant metal from the release chamber together with any feed material, intermediate reaction products, and final reaction products, and to hold any unreacted materials in contact with the liquid reactant metal for a sufficient period of time to ensure the desired reactions.
In another variation of the invention, the collection area is not necessarily positioned so that a flow of liquid reactant metal through the release chamber or any downstream chamber provides the desired contact with the liquid reactant metal. In this form of the invention, feed materials from the container, intermediate reaction products, and perhaps some final reaction products are first collected in the collection area and then transferred from the collection area by suitable means into a separate reaction chamber. The separate reaction chamber and transfer structure forms the treatment arrangement in this form of the invention. The separate reaction chamber may be within the containment vessel in which the feed material was originally released and thus employ the same type of liquid reactant metal used in the release chamber. Alternatively, the separate reaction chamber may comprise a completely separate liquid reactant metal reactor using a second liquid reactant metal. In either alternative of the separate reaction chamber, some of the desired reduction reactions and the destruction of the container may still occur in the release chamber or in a reaction chamber downstream from the release chamber in a direction of reactant metal flow.
In both forms or variations of the treatment system described above, the apparatus includes an output chamber and reaction product removal arrangement for removing gasses, solids, and liquids from the output chamber. Solids comprising slag collecting at the surface of the liquid reactant metal in the output chamber and some liquids are preferably removed by a suitable skimming system. Gasses collect above the liquid reactant metal in the output chamber and are drawn off through a suitable vent line for further processing to recover the various constituents in the gases. Liquid taps may also be included in the output chamber for removing liquids which separate from the liquid reactant metal in the output chamber.
The slag removed from the output chamber may include metal salts such as aluminum chloride, unreacted minerals released from the feed material, and dross made up of oxides of the reactant metal. It has also been found that the slag may include a substantial fraction of reactant metal and other metals caught up and solidified with the other slag materials. In order to recover the reactant metal and other materials from the slag, the invention includes a slag processing device arranged to receive slag from the output chamber of the liquid reactant metal reactor. This slag processing device may comprise a second liquid metal reactor connected to receive the slag removed from the output chamber. This second liquid metal reactor may be entirely separate from the reactor receiving the containerized feed material or may be incorporated in the container treatment system in order to share the same liquid reactant metal. The treatment of slag in a second reactor reclaims solidified reactant metals and other metals from the slag. Alternatively to a second liquid metal reactor, the slag processing device may comprise a heating device adapted to heat the slag to selected temperatures in order to selectively melt desired materials out of the slag. Solidified reactant metal is recovered from the slag by holding the slag at a temperature just above the melting point of the reactant metal after first removing lower melting point materials.